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The Flawed Science of Antibody Testing for SARS-CoV-2 Immunity, JAMA, 21 Oct 2021
The SARS-CoV-2 serology tests that eventually received FDA Emergency Use Authorization (EUA) have demonstrated high sensitivity and specificity, but that accuracy is for detecting antibodies. Their ability to predict protection against the virus based on those antibodies hasn't been proven. Plus, the FDA cautioned that some tests detect antibodies the immune system likely produces only after natural infection with the virus. Depending on the assay, people who weren't previously infected could test negative for antibodies despite having vaccine-induced immunity.

Therefore, the agency in its May 19 communication stated that "results from currently authorized SARS-CoV-2 antibody tests should not be used to evaluate a person's level of immunity or protection from COVID-19 at any time, and especially after the person received a COVID-19 vaccination."


FDA finds 3 COVID-19 tests that fail to detect the omicron variant, 16 Dec 2021
The agency on Wednesday updated its list of tests impacted by virus mutations. While FDA continues to gather additional information and work with the three manufacturers to address these issues, it recommended the diagnostics not be used by clinical laboratory staff and healthcare providers.
by Cat on Tue Dec 21st, 2021 at 06:50:15 PM EST
The struggle between authoritative figures to rationalize GAPS in virology, bio statistical models, and both pharmaceutical and non-pharmaceutical interventions in activites of daily life (ADLs) purporting TIA based on COVID antibody test frequency and accuracy (medical surveillance") continues.

'This was the moment': CDC defends altered guidance amid Omicron surge

The multi-part defense from Walensky -- who appeared on at least five TV networks on Wednesday morning -- comes as the Biden administration has begun instituting new guidance and considering further restrictions to curb an EXPLOSION of U.S. coronavirus cases caused by the Omicron variant.
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"We have seen relatively low rates of isolation for all of this pandemic. Some science has demonstrated less than a third [?!] of people are isolating when they need to," Walensky told CNN.
[...]
"In the context of the fact that we were going to have so many more cases -- many of those would be asymptomatic or mildly symptomatic -- people would feel well enough to be at work, they would not necessarily tolerate being home ["self-isolation," "social distancing," "quarantine"], and that they may not comply with being home, this was the moment that we needed to make that decision," Walensky told CNN.
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"It's frankly reckless to proceed like this," Eric Topol, founder and director of the Scripps Research Translational Institute, told The Associated Press on Tuesday. "Using a rapid test or some type of test to validate that the person isn't infectious [sic] is vital."
[...]
As for the more accurate Covid-19 [RT-]PCR tests RNA sequence assays -- which use real-time polymerase chain reaction technology and generally take hours to produce results -- Walensky said they were not included in the new CDC guidance because they can show positive results up to 12 weeks after initial infection.

"That is not going to be helpful," Walensky told NBC. "You're not going to be transmitting during all of that period of time."

memorable quote
"We do know that the some rapid antigen tests may not perform as well as it had for prior variants -- the Alpha variant and the Delta variant -- but it's still picking up quite a bit of infection," Walensky said.
selecting the correct tool for the job: isolating emergence and frequency of SARS-CoV-2 variants
FDA: Antigen tests may have reduced sensitivity detecting Omicron
reference
SARS-CoV-2 Viral Mutations: Impact on COVID-19 Tests, Content current as of 12/28/2021
On September 23, 2021, the FDA revised the EUAs of certain authorized molecular, antigen, and serology tests to establish additional Conditions of Authorization in response to the continued emergence of new variants of SARS-CoV-2. [...] These conditions require test developers to update their authorized labeling and evaluate the impact of SARS-CoV-2 viral mutations on their test's performance, among other things.
from laboratory "controlled" to "live" samples
RADx recently performed preliminary studies evaluating the performance of some antigen tests using patient samples containing live virus, which represents the best way to evaluate true test performance in the short-term. Early data suggests that antigen tests do detect the omicron variant but may have reduced sensitivity.

Prior to completing these live virus tests, RADx conducted initial laboratory tests using heat-inactivated [wtaf] samples for some of the currently available antigen tests, which were able to detect the omicron variant, with similar performance when detecting other variants. Heat-inactivated samples are patient samples with omicron variant that have been heat-treated so that the virus is no longer ["]live["]. Heat-inactivated samples are the best available option when patient samples with live virus are not available.

Tests with Detection Patterns that May Be Associated with the SARS-CoV-2 Omicron Variant (As of 12/22/2021)
The detection pattern, showing the drop out, or failure of the affected target, may help to signal the presence of the omicron variant in a patient sample with a positive result so that sequencing can be considered to characterize the variant.

Potential Impact Sampling Errors: Since these tests are designed to detect multiple genetic targets, the overall test sensitivity should not be impacted. The pattern of SARS-CoV-2 detection with one gene drop out may provide a signal that the omicron variant may be present so that sequencing can be considered to characterize the variant. However, testing positive for SARS-CoV-2 with one of these tests does not mean an individual is infected with the omicron variant. Further, not all patient samples with the omicron variant display a mutation that leads to a gene drop out. Therefore, the omicron variant may still be present without a gene drop out detection pattern.

supra "The Flawed Science of Antibody Testing for SARS-CoV-2 Immunity," JAMA, 21 Oct 2021
by Cat on Wed Dec 29th, 2021 at 11:40:03 PM EST
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